# Design Closed Circuit Introduction, May 2012

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Design Closed Circuit Introduction, May 2012
1.) Presentation about Design Closed Circuit with focus on overview and functionality of the closed circuit components target is to know which components are necessary for full function of closed circuit, which will be build up step by step in an animation furthermore you will get information which other components (heat exchanger, reservoir, kinds of fluid, filter) are necessary to fulfill oil requirements (3) Presentation created by: Marc Peter (3) Date of creation: July 2012 Introduction, May 2012

Functionality of components
Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger 1.) Here you can see the agenda of this presentation at first we will see step by step how to design a closed circuit in an animation, were you have to fill a handout with questions then I will give a review, were we will work out the functionality of components based on the sytem overview and the handouts the last four chapters muck about hydraulic fluid, cleanliness and filtration, reservoir and heat exchanger to fulfill fluid requirements Basic Hydrostatic (closed circuit)

Functionality of components
Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger 1.) we will see in an animation step by step how to design a closed circuit in an animation, were you have to fill a handout with questions then will describe the transmission characteristic and the connection between displacements, speeds and torques 2.) Hand out the Handouts with questions, please fill out, answer the questions, will help to find out functionality of components in next chapter 2.) Open Animation Basic 3 Basic Hydrostatic (closed circuit)

1. System Overview Hydrostatic Transmission
Continuously variable speed w/o loss of traction A B Speed [km/h] T r a c t i v e F o [ N ] Pump Ratio Motor Ratio Installed Engine Power hydrostatic transmission - source 1 - 2.) Question (1st hide the characteristic): How looks like the characteristic of hydrostatic transmission? Work on Flipchart: draw at first the both axis, work together with participants 1.) See the behavior of the hydrostatic transmission, right side, transmit full installed engine power (for proportional motor control) A: Pump Ratio is the range were motor is at max displacement and pump displacement changes from min displacement (0° at 0 km/h) to max displacement (18° (H1P) at max working speed); -> working mode B: Motor Ratio is the range were pump is at max displacement and motor displacement changes from max displacement (32° (H1B) at max working speed) to min displacement (>=6° (H1B) at max travelling speed); -> travel mode

1. System Overview Hydrostatic Transmission
Motor output torque and speed depends on pump and motor displacement Speed of hydrostatic transmission is reciprocal to displacements Torque is proportional to displacements 1.) See picture of hydrostatic transmission input is Torque TP, Speed nP and both build up Power PP (installed engine power) Pump Displacement VgP, Pump Flow QP, Motor Flow QM, this distinction cause of volumetric losses, delta pressure also called system pressure Δp is difference between low and high pressure side Motor Displacement is VgM output of motor is Torque TM, Speed nM and both build up output Power PM which is directed to a gear and wheels or wheels were it‘s transmit into tractive force Again: Motor output toque and speed depends on pump and motor displacement 2.) Question (hide the equation box): is the speed ratio reciprocal or proportional to displacements? & is the transmission ratio reciprocal or proportional to displacements? (work on flipchart, write down speed and transmission ratio) 2.) Show text and the equations box

Functionality of components
Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger 1.) now I will give a review, were we will work out the functionality of components based on the system overview and the handouts Basic Hydrostatic (closed circuit)

2. Functionality of Components Integrated Charge Pump
1.) You can see the closed circuit again, with pump, motor, integrated charge pump, charge relieve valve, charge check valve, high pressure relieve valves, Loop Flushing system, filter and heat exchanger (show them again) Here we start with the charge pump 2.) What would happen when the charge pump is missing? – mainly cause of loop flushing and Leakage the closed circuit would be drained and system would be oil devoid after short time (sequence: system damage) 2.) Question please describe: is charge pump a fixed or variable displacement pump?- fix pump, see next slide

2. Functionality of Components Integrated Charge Pump
Charge pump is a fixed displacement pump (gerotor-type) which is directly connected to the pump input shaft Charge pump displacement should be sized to approximately 10% of whole system displacement (pump and motor(s) displacements) in most applications 1.) fixed displacement gerotor-type pump directly connected to pump input shaft, means flow directly depended by pump input speed 2.) Do you think discharge in view to system is correct, why not, why yes? – Yes: For Pump itself; No: For system it‘s charge 1.) Sizing of pump should be in most applications 10% of whole system displacement (motor plus pump displacement) 2.) Example Calculation on Flipchart: Pump H1P068; Motor H1B80: 68cc+80cc->148cc->14,8cc for charge pump (H1P068 only 14 or 17cc available), choose 14 cc here for H1P Pump H1P089; 2 x Motor H1B80: 89cc+2x80cc->249cc->24,9cc for charge pump (H1P068 only 20 or 24cc available), choose 24 cc here for H1P 1.) also possible to use external charge pump, for example if largest available internal charge pump to small?????????? 1.) important: please pre initial operation to test charge pump sizing before release?????????????

2. Functionality of Components Charge Pump - Functions
Charge Pump flow rate functions: Replenish leakage oil of pump and motor Replenish loop flushing oil through the flushing valve Provide flow for the servo control systems Provide flow for auxiliary circuit functions e.g. parking brake release Charge Pump pressure functions: Maintain low loop pressure Provide sufficient pressure to activate the servo control systems 1.) Flow Rate Functions, Control system: means motor and pump control Pressure Functions: Low loop pressure is necessary, to prevent damage of hydrostatic transmission cause of cavitation???????? 3.) Additional Information: circuit leakage depends on: pressure speed temperature pump or motor angle

2. Functionality of Components Charge Pressure Relief Valve
1.) See the Charge Pressure Relief Valve in the system 2.) Question: What is the task of this valve what would happens w./o. this valve?

2. Functionality of Components Charge Pressure Relief Valve
Charge pressure relief valve is necessary to maintain low loop pressure Protects the charge pump by limiting the charge pressure Excess charge pump output flow is directed into the pump case 1.) Typical setting range is 18 to 34 bar it depends on auxiliary systems like brake system or further control systems Valve is permanent active, always an overage 2.) Animation H1 Pump “Charge Pressure Relief”: show that permanent active when pump flow exist

2. Functionality of Components Charge Check Valve
1.) See the Charge Check Valve in the system it‘s a simplified view, function here like a sphere check valve 2.) What would happens w./o?

2. Functionality of Components Charge Check Valve
It protects the charge pressure system (charge pump), otherwise a backflow from high pressure side will damaged the charge pump 1.) Function is to protect charge pump from high pressure and permit flow to low pressure side Pictures show two conditions, Circuit Loop at low and high pressure, Low Pressure permit flow at high pressure it will close the flow connection 2.) Animation H1 Pump “Charge”: say that permanent active when pump flow exist and is on low pressure, includes also High Pressure Relieve valve function, see later

2. Functionality of Components Loop Flushing System
1.) See the Loop Flushing System in the closed circuit 2.) Question: Which two components include the loop flushing system? – LF Relief Valve and Shuttle Valve (write on Flipchart) Question: Why it isn‘t enough to use only LF Relief Valve? – Otherwise no Protection before High Pressure, which would connected to the motor case, it’s pressure is limited Question: Why we need a loop flushing? – Cause of heat in the system, cooling down Question: Reason for the heat? – efficiency losses, mechanical: bearings of pistons in cylinder block, friction of bearings, splash losses, volumetric: leakage, functional leakages on High Pressure Relief Valve or on charge pressure relief valve (write down on flipchart)

2. Functionality of Components Loop Flushing System
Loop Flushing is necessary because of cooling requirements and contamination removal of system circuit The LF-system removes fluid from the low pressure side of the closed circuit system Loop Flushing valves are available with different flow rates to optimize flush flow requirements in all system operating conditions 1.) Loop Flushing System is integrated in motor, 2 motor concept, when only one motor with LF system, please flush second motor (two case drain ports, flush from down to up) 2.) Review to flipchart, see 1st to facts 1.) different flows of LF relief valve, H1B: 5, 10, 15, 20, 30, 40 and 50 l/min for H1B availability depends on motor size, see Master Model Code of motor 2.) Show Animation H1 Motor „Loop Flushing“ Hand out the model (assembled and de assembled)

2. Functionality of Components High Pressure Relief Valve (HPRV)
1.) See HPRV in the closed circuit 2.) Question: What is the main task of the HPRV? – Limit the maximum pressure, protect system components before damage Question: What would happen, when HPRV is permanent active (means motor can‘t absorb flow cause of to high load)?- Flow losses - overheating of the system Question: What could be an action to prevent system before that effect? – destroke of the pump, decrease pump flow

2. Functionality of Components High Pressure Relief Valve (HPRV)
High pressure relief valves are needed in hydrostatic transmission systems to limit maximum pressures Pressures above the product ratings will damage the transmission HPRV protect pumps, motors, hoses and other system components 1.) HPRV to limit maximum pressure, to protect the components 2.) Animation H1 Pump „High Pressure“: Same Valve for charge check valve and high pressure relief valve function 2.) Question during Animation: What could be an action to prevent system before that effect? – destroke of the pump, decrease pump flow, see Animation “Pressure Limiter”

2. Functionality of Components Pressure Limiter
Pressure Limiter is a non dissipative high pressure control Limits the heat generated in the system when pressures are too high PL changes the displacement of the pump in response to high system pressure 1.) PL-System is non dissipative 2.) Question: What means Dissipative? - a system when there is continuous extract of energy 1.) limits generated heat, when pressures are to high Unlike a relief valve, the PL changes the displacement of the pump in response to high system pressure 3.) When the system pressure exceeds the PL setting - The PL ports control fluid to the servo system - The pump destrokes the swash plate to the position required to maintain the set system pressure 3.) The Multifunctional Valve of Series 90 Pump includes 4 functions: - System Pressure Limiter - Charge Check - System Pressure Relief - Bypass Valve

2. Functionality of Components Bypass
Bypass function allows an internal connection to be made between the two loops in the hydrostatic transmission Function allows the vehicle to be moved without the engine running Allows for disabled vehicles to be loaded onto a trailer or moved off the road Intended to be for slow, short durations otherwise the hydrostatic transmission can be damaged 1.) bypass function allows an internal connection between both loops, 2.) Animation H1 Pump „Bypass“: realize bypass by unscrewing of the HPRV maximal three revolutions, otherwise danger of leakage 2.) Hide Text; Question: What is the reason for that function? – open bypass for, see next facts 1.) for vehicle to be moved without engine running (pump is definite) and motor would be drivin by output drive vehicle by trailer or moved off the road drive slow, otherwise hydrostatic transmission can be damaged

Functionality of components
Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger 1.) Next Topic are Hydraulic Fluids 2.) Question: Which task have Hydraulic Fluids in a hydrostatic transmission? – Write Down the Answers on Flip Chart 2.) Question: Which Hydraulic Fluids do you know? – Write Down the Answers on Flip Chart Basic Hydrostatic (closed circuit)

3. Hydraulic Fluids What do you know about Hydraulic Fluids?
Sun Dirt Water Air Blood Alcohol 2.) Question: What do you know about Hydraulic Fluids?, Please try to abstract by following pictures 1.) Sun: Heat; Water: Problem if using Water is: corrosion, lubrication attitude,...; Air: Air in Oil will cause kavitation; Blood: is what oil is for the body, for the hydrostatic transmission; Dirt: Contamination, also bad for blood in the body (alcohol), has to be filtered, in Body by the liver; also a problem for body as for hydrostatic transmission to work with two different kinds of fluid/blood

3. Hydraulic Fluids Overview Hydraulic Fluid Groups
Mineral oil based hydraulic fluids Biogradeable hydraulic fluids Syntetic ester (HEES) Rape oil alkaline (HETG) Fire resistance fluids ATEX Regulation 1.) See the groups of hydraulic Fluids, first one, the mineral oil based are most commonly used 1.) second are biogradeable fluid, Synthetic ester (HEES) recommended (mechanical attributes similar to Mineral oil based hydraulic fluids); Rape oil alkaline (HETG) not recommended (not high temperature resistence) 1.) last one are the flame resistance fluids, for ATEX Regulation (European Regulation for explosion protection)

3. Hydraulic Fluids Recommended Hydraulic Fluids
Find recommended Hydraulic Fluids for Sauer-Danfoss hydrostatic components in Technical Literature* Fluids meeting the technical literature requirements will very likely provide acceptable unit life field testing is the only truly indication of fluid performance Sauer-Danfoss warranty claim policies do not apply for fluid related damage *: “Hydraulic Fluids and Lubricants Technical Information”; page 20 1.) SD recommend several oils in it’s technical literature on page 20 1.) fluids which are meeting the requirements of technical information provide acceptable unit life 1.) field testing to indicate fluid performance is recommended 1.) no warranty for fluid related damage

3. Hydraulic Fluids Physical Behavior
Viscosity Viscosity grade (VG) Depends on temperature and pressure Compromise between flow losses and leakage Density 1.) Most important attribute of hydraulic fluid are viscosity and density, they are depending on temperature and pressure 1.) viskosity is a compromise between flow losses and leackage

3. Hydraulic Fluids Physical Behavior
Temperature-Behavior Pressure-Behaviour kinematic Viscosity kinematic Viscosity 1.) You can see the definition by ISO VG 1.) the value is defined as kinematic viscosity at 40°C Temperature Temperature

3. Hydraulic Fluids Viskosity and Temerature Limits
Viscosity and temperature limits in the table “Viscosity and temperature limits” in technical information* are to be observed Under normal operating condition it is recommended to keep the temperature in the range of 30 °C to 60 °C Rule of thumb: fluid temperature increase from 80 °C [176 °F] to 90 °C [194 °F] may reduce fluid life by 50 % *: “Hydraulic Fluids and Lubricants Technical Information”; page 19 1.) limits for viscosity and temperature for Sauer Danfoss Products are defined in the technical literature 1.) recommend to keep temperature between 30 and 60°C, over 90°C reducing of life time by 50%

Improvement of oil attributes Viscosity-temperature behavior Wear protection Corrosion protection Ageing resistance Foam prevention Bond to dirt particles 1.) Additives can improve oil attributes 1.) change Viscosity-temperature behavior for optimal machine requirement 1.) wear protection of slide part surfaces 1.) corrosion protection, ageing resistance 1.) foam prevention, to decrease quota of air in the oil, cause of cavitation 1.) bond to dirt particles

3. Hydraulic Fluids Selection Criteria
Manufacturer‘s instructions Release of diverse oils Depends on system Application (vehicle, temperature conditions) Fill rate Application environment Climate Area of application (i.e. environmental, flammability regulations, etc.) 1.) Criteria for Oil Selection, SD instructions, system (temperature, vehicle), application environment

Technical Information “Hydraulic Fluids and Lubricants” (520L0463) Technical Information “Experience with Biodegradable Hydraulic Fluids” (520L0465) 1.) Further Details you can find on Technical Information “Hydraulic Fluids and Lubricants”

Functionality of components
Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger 1.) Know you will see how we can reach required cleanliness Basic Hydrostatic (closed circuit)

4. Filtration Contamination
Sources of contamination: Installation System components Fill oil Repair of a unit Types of contamination: Metal Synthetic materials Organic materials Plastic Water Etc. Scratches on Piston Shoe 2.) Question: What could be a source of contamination? 1.) sources could be auxiliary components like reservoir, fittings, hoses, valves, ..., big effort on our part to prevent before contamination, especially for our components 1.) Fill oil into the hydrostatic transmission or repair of a unit 1.) Change of auxiliary components in the vehicle 1.) Types are metal, plastic, water, foreign fluids, plastic 1.) result could be scratches, wear on sliding part surfaces or damage of the machine, cause of failure of the bearings, pistons, piston shoes or decreasing efficiency (leakage, friction)

4. Filtration Cleanliness Classes
ISO : Specification of three cleanliness classes correlated to particle size ≥4; ≥6; ≥14 [μm] Example: ISO 18/16/13 number of particles 1/ml cleanliness classes (ISO 4406) 0,01-0,02 1 0,02-0,04 2 0,04-0,08 3 0,08-0,16 4 0,16-0,32 5 0,32-0,64 6 etc. 40-80 13 80-160 14 15 16 17 18 19 20 21 22 23 24 1.) to define a maximal contamination level, there is cleanliness class definition on ISO 1.) describes number of several particle sizes (greater 4, 6 and14 µm) per ml 1.) see example 2.) Question: What means ISO 18/16/13? – write down on Flipchart 2.) 18  particle ≥4μm 2.) 16  particle ≥6μm 2.) 13  particle ≥14μm

4. Filtration Cleanliness Classes
Sauer-Danfoss recommends the cleanliness classes below for different applications* Product Required cleenliness class ISO Steering components with open center 22/20/17 Orbital motors 22/20/16 Steering components with LS and closed center 21/19/16 Proportional spool valves Axial + radial piston pumps and motors 22/18/13 Gear pumps and motors Cartridge and electrohydraulic valves 18/16/13 1.) required cleanliness by Sauer Danfoss for the axial piston pumps and motors is 22/18/13, you can also see in the technical information 1.) the required maximum class at machine start up is 25/22/17 Maximum class at machine start up 25/22/17 *: “Design Guideline for Hydraulic Fluid Cleanliness Technical Information” (520L0467), p. 13, Spreadsheet: “Fluid cleanliness requirements according to product“

4. Filtration Kind of Filtration
Partial flow filtration + Small filter - Partial backflow of oil w/o filtration - Charge pump unprotected (pre-filtration necessary) 1.) Now we will see how to reach cleanliness classes by filtration 1.) 1st kind of filtration is partial flow filtration it’s a press filtration; filter before charge check valve, charge pump relief valve is the bypass to the filter 1.) a part of the flow, flow along the charge pump relief valve to the pump case 1.) Advantage: small filter 1.) Disadvantage: Particular backflow of oil w/o filtration, Charge pump unprotected (pre-filtration necessary)

4. Filtration Kind of Filtration
Full flow filtration + Complete oil filtration + Small filter - Charge pump unprotected ( pre-filtration necessary) 1.) Second type is the flow filtration, it‘s like the partial flow filtration a press filtration, has the advantage of complete oil filtration and small filter 1.) Disadvantage is, that charge pump is unprotected

4. Filtration Kind of Filtration
Suction filtration + Charge pump protected - Large filter surface necessary - Disadvantageous at low temperature 1.) third is the suction filtration, where charge pump is protected, it‘s in view to start up important 1.) disadvantages are large filter surface necessary and could be a problem at low temperature cause of negative pressure

Functionality of components
Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger 1.) Next auxiliary component is the reservoir 2.) Question: What do you imagine could be the tasks of the Reservoir? See next slide Basic Hydrostatic (closed circuit)

5. Reservoir Overview Art der Filterung
Tasks: Fluid reservoir Ensures there is enough oil for hydraulic system Cooling Separates dirt, water and air Assures smooth fluid flow (laminar flow) at suction 1.) main task is that it is a fluid reservoir(for backflow from heat exchanger of the loop flushing flow, for leakage, ...) 1.) ensure that there is enough oil for hydraulic system ( Extending large cylinders, Operating on slopes) 1.) Cooling – not primary cooling for hydraulic system 1.) Separates dirt, water and air for filtration, to reduce allotment of air in the oil 1.) Assures smooth fluid flow (laminar flow) at suction of the Pump

Functionality of components
Main Menu System Overview Functionality of components Hydraulic Fluids Filtration Reservoir Heat Exchanger 1.) Last topic is the „Heat Exchanger“, to cooling down the hydrostatic transmission system 2.) Question: Do you know what is the reason for heat? – Bearings, Pistons -> Friction; volumetric losses or HPRV Basic Hydrostatic (closed circuit)

6. Heat Exchanger Function and Type
Removal of hydraulic-system heat Prevents overheating of oil Ideal oil-temperature should be 60 to 80°C Construction type in mobile hydraulic Oil-air-heat exchanger Oil-air heat exchanger 1.) Task is to remove hydraulic system heat, ideal oil-temperature should be 60 – 80°C 1.) normal construction is the oil-air heat exchanger, see the picture

6. Heat Exchanger Design Criteria
vehicle 1.) To better understand the different steps of choosing and implementing a cooling system and at least a fan drive system we have to look at this development process. 1.) The vehicle manufacturer has to design his machine and to choose the right size of engine. 1.) Together with other suppliers he has to determine the cooling demand for his machine and to decide which size of cooler and fan he wants to use. 1.) After this decision he has to contact potential fan drive system suppliers and to deliver necessary data for the design of the system. 1.) The vehicle manufacturer will remain responsible for the layout of the cooling system but anyway it will be necessary and at least helpful to know and understand the different influences and relations on cooling systems like fan diameter, fan speed, pressure, air flow and others. engine cooler fan SD FD system S-D SAE Fan Drive Training/ I - Introduction, Basic Fan Drive Training, Oct 2008.ppt

6. Heat Exchanger Sauer-Danfoss Fan Drive
example: closed circuit 1.) See an example for an cooling down system 1.) separate fan drive motor

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